| Document and Entity Information | Oct. 16, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 16, 2023 |
| Entity File Number | 0-25165 |
| Entity Registrant Name | GREENE COUNTY BANCORP, INC. |
| Entity Central Index Key | 0001070524 |
| Entity Incorporation, State or Country Code | X1 |
| Entity Tax Identification Number | 14-1809721 |
| Entity Address, Address Line One | 302 Main Street |
| Entity Address, City or Town | Catskill |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 12414 |
| City Area Code | 518 |
| Local Phone Number | 943-2600 |
| Title of 12(b) Security | Common Stock, $0.10 par value |
| Trading Symbol | GCBC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
